IBM 5150 Hardware Reference Manual page 124

+AO-9
+AEN
~
-lOW
-lOR
-DACK2
~
+T/C
+RESET
+DRQ2
~
+IRQ6
(Adapter Input, Load: 1 74LS)
These ten lines form an address bus by which a
register is selected to receive or supply the byte
transferred via lines DO-7. Bit 0 is the low-order bit.
(Adapter Input, Load: 1 74LS)
The content of lines AO-9 is ignored if this line is
active.
(Adapter Input, Load: 1 74 LS)
The content of lines DO-7 is stored in the register
addressed by lines AO-9 or DACK2 at the trailing
edge of this signal.
(Adapter Input, Load: 1 74LS)
The content of the register addressed by lines AO-9
or DACK2 is gated onto lines DO-7 when this line
is active.
(Adapter Input, Load: 2 74LS)
This line active degates output DRQ2, selects the
FDC data register as the source/destination of bus
DO-7, and indirectly gates T / C to IRQ6.
(Adapter Input, Load: 4 74 LS)
This line and DACK2 active indicates that the byte
of data for which the DMA count was initialized is
now being transferred.
(Adapter Input, Load: 1 74LS)
An up level aborts any operation in process and
clears the Digital Output Register (DOR).
(Adapter Output, Driver: 74LS 3-state)
This line is made active when the attachment is ready
to transfer a byte ofdata to or from main storage. The
line is made inactive by DACK2 becoming active or
an I/O read of the FDC data register.
(Adapter Output, Driver: 74LS 3-state)
This line is made active when the FDC has com ­
pleted an operation. It results in an interrupt to a
routine which should examine the FDC result bytes
to reset the line and determine the ending condition.
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